Epicyclic gearboxes



Aug. 6, 1957 v J, E, sTUBBlNc-:s `El' AL 2,801,552

EPIcYcLIc GEARBOXES Filed Mrch 12. 1954 2 sheets-sheet 1 All@ '6, 1957 J. E. s'rUBBxNGs ErA1 2,801,552

EPICYCLIC GEARBOXES Filed March 12, 1954 2 Sheets-Sheet 2 United States Patent C EPICYCLIC GEARBOXES John Eric Stubbings, Churchover, near Rugby, and Archie John Hirst, Leicester, England, assignors to The British Thomson-Houston Company Limited and Metalastik Limited, both British companies Application March 12, 1954, Serial No. 415,964 Claims priority, application Great Britain March 16, 1953 4 Claims. (Cl. 74-801) This invention relates to an epicyclic gear assembly, and particularly to a means of resiliently mounting the internal gear annulus.

In an epicyclic gear assembly it is not the absolute position of the internal gear annulus but its relative position with respect to the planet wheels with which it meshes which is important, and it is desirable that it should be allowed limited freedom to locate on the planet wheels with which it meshes. Nevertheless rotation of the annulus must be prevented, and it is with the mounting of the annulus to meet these conditions in some measure that the invention is concerned.

The object of the present invention is to mount the internal gear annulus of an epicyclic gear assembly in such a manner that the resistance to rotational motion is greater than the resistance to radial motion.

According to the invention the normally lixed gear annulus is located with relation to an outer casing through the intermediary of two or more links having connections to the annulus and extending substantially at right-angles to the radius from the centre of the annulus to their connections to the annulus, the ends of the links remote from the annulus being anchored to the casing, resilient material being interposed in the connections at at least one end of each link.

in the preferred arrangement the gear annulus is located on the casing through the intermediary of three or more links having their connections to the annulus equally spaced on a pitch circle concentric to the pitch circle to the gear, the links extending approximately tangential to the pitch circle and having their connections to the casing equally spaced from one another, the connections of the links to the annulus and to the casing being effected through resilient material.

The invention will now be described with reference to the accompanying drawings, in which Fig. l shows an end view of a preferred arrangement incorporating the invention. Fig. 2 is a detail showing the connections of the ends of the links to the casing, and Figs. 3 to 6 show diagrammatically other arrangements of links which may be adopted for connecting the gear annulus to the casing.

Referring tirst to the arrangement shown in Figs. 1 and 2, the casing is shown at 1 and the internal gear annulus at 2. In this arrangement are shown four links 3 connecting the annulus to the casing. At each end of the links are bearings made up of three parts, a metal outer casing 4, a resilient member 5, which could conveniently be rubber and a metal inner sleeve 6, all of which could be bonded into a single part. The sleeves are fitted on to pins 7, four of which are attached to the casing 1 and four to the annulus 2. The points of connection of the ends of the links to the casing and annulus, respectively, are equidistantly disposed so that the links extend in the same direction approximately tangentially from the pitch circle on which their inner connections are located; each link is thus normally at right angles to each adjacent link.

It is obvious from the diagram that the resistance to rotation of the annulus with respect to the casing is prolCC vided by the compression of the rubber intall the bushes, whereas considerably less resistance is oifered to any radial force, the ratio of these resistances being approximately 2:1.

Referring now to Fig. 3, we have shown a further disposition of links which may be adopted. In this case the gear annulus 2 is again furnished with four links connecting it to the casing, the links having their connections to the annulus equally spaced, as in the arrangement shown in Fig. 1. Instead, however, of all the links extending tangentially in the same direction from the annulus, as in the arrangement shown in Fig. 3, links 8 and 9 extend in a similar manner to the links shown in Fig. l, whereas links 10 and 11 now extend tangentially from the annulus in the opposite direction from that occupied by links 8 and 9. The connection of the outer end of link 11 is made to an ear 12 which also serves as a support for the outer endof the link 9. In this arrangement, as in the Fig. Vl arrangement, the ratio of tangential to radial resistance to movement is again 2:1.

Fig. 4 shows a further arrangement in which four equally spaced ears 13` are provided on the annulus to form connections through the links which extend to four equidistantly spaced ears 14 on the annulus. `In this arrangement each ear on the annulus and on the casing forms a connecting point for the ends of two links thus forming an arrangement similar to Fig. 1 but in which all the links are duplicated.

Fig. 5 shows a further arrangement in which three equidistantly spaced ears 15 are provided on the casing and a similar number of ears 16 on the annulus. In this arrangement, a single link 17 has its outer ends connected, preferably through resilient material, to adjacent ears 15 on the casing while its mid-point is connected through resilient material to the ear 16 on Vthe annulus. Link 17 thus resists rotation of the annulus by compression and tension respectively in its opposite halves while resisting rotation radially by bending. The two remaining links 18 are connected in a manner similar to that indicated in Figs. 3 and 4.

A modified arrangement of that shown in Fig. 5 is shown in Fig. 6 in which the annulus is supported by only two links. In this case two diametrically spaced ears 19 are provided on the gear annulus and four equidistantly spaced ears 20 on the casing. Two links 21 similarly arranged to the link 17 on Fig. 5 now support the annulus between them, the links being connected at their midpoints to the ears 19 through resilient material. Radial movement of the annulus is thus resisted partly by bending of the two links 21 and partly by tension or compression in those links, while rotational movement is resisted by tension or compression in the links.

The links oder very little resistance to axial or endwise movement at any point on the periphery. The flexibility due to angular movement of the axis of the inner sleeve relative to that of the outer can be added to the exibility due to axial shear of the rubber. Hence the axis of the exibly mounted annulus can be displaced easily through a small angle to maintain more uniform tooth pressure over the face width.

The bushes should be preferably of the type described in British Patent No. 581,464. If the bushes are in natural rubber, they may be provided with synthetic rubber oil resistant seals at the ends.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. An epicyclic gear comprising a casing, a sun wheel rotatably mounted in said casing, a plurality of planet wheels uniformly disposed about said sun wheel and in engagement therewith, said planet wheels being mounted on a carrier rotatable within said casing, an internal gear annulus engaging the said planet wheels, and means for QJ resisting 'rotation 'of said gear annulus with respect to said casing while permitting limited translation there-within, said means comprising a plurality of links each extending fromyan individual pivotal connection on said gear annulus'toward's said casingand pivotallyconnect'ed at ltheir remote ends 'to said casing, the axes ofthe pivotal connections of "said links to said gear annulus and said casing being equi-angularly disposed and the axes Vof said pivotal'c'onnectios between said `links and 'said annulus being Vlocated on acommon pitch circle coaxial with said annulus, said links extending substantially tangential to said 'pitch 'circle and 'resilient means interposed between said points of pivotal connection on said gear annulus andsaid easing whereby to permit of limited displacementof said gear annulus with respect to'said casing without'perinit'ting'relative rotation between said gear annulus and'said'c'asing. n.

2. An epicyelic 'gear assembly comprising an outer casing, "an internal gear annulus mounted within said casing, fa s url 'wheel rotatably mounted within said casing, a plurality of planet wheels engaging said sun wheel and saidlgeanannulus, a carrier for said planet wheels, said carrier Abeing mounted rotatably within said casing, the mounting for'said gear annulus'within said casing cornprising atleast three links extending between said casing and said vgear annulus and pivotally connected to said casing and said annulus at their opposite ends, said links extending in a direction substantially at right angles to the radius from the centre of said gear annulus to their connections therewith, resilient material being interposed in the connections at at least one end of each of said links.

3. An epicyclic gear assembly comprising an outer casing, an internal gear annulus mounted within said casing, a sun wheel rotatably mounted within said casing, a plurality of planet wheels engaging said sun wheel and said gear annulus, a carrier for said planet wheels, said carrier being mounted rotatably within said casing, the mounting for said gear annulus within said casing comprising four links extending each from a pivotal connection on said gear annulus in a direction substantially normal to the radius from the centre of said gear annulus to said points of pivotal support, the ends of said links remote from their connection to said gear annulus being pivotally connected to said casing, resilient means being interposed in the connections at at least one end of each of said links.

4. An epicyclic gear as claimed in claim 3 in which said links are symmetrically arranged around said gear annulus so as to 'extend in the 'same direction from said annulus 20 towards said casing.

Retarciees Cited in the le of this patent 'UNITED STATES PATENTS 25 2,407,975 Christian Sept. 24, 1946 2,500,393 Williams Mar. 14, 1950 FOREIGN PATENTS 10,359 Germany July 14, 1880 345,178 Germany Dec. 6, 1921 if. f lira- 

